This invention employs 1,2-alkyl diols of from C4 to C10 (4 to 10 carbon atoms forming the alkyl) in otherwise conventional aqueous inks to eliminate bleeding of inks of different colors. The use of alcohols in such inks is conventional, as illustrated in U.S. Pat. Nos. 5,207,824 to Moffatt et al, 5,196,056 to Prasad and 5,196,057 to Escano et al, but not the use of 1,2-alkyl diols of from C4 to C10. U.S. Patent No. 5, 165,968 to Johnson et al lists 1,2-pentane diol as unacceptable for the inks of that patent.
U.S. Pat. No. 5,141,558 to Shirota et al teaches the use of a wide variation of triols in such inks to improve anti-feathering, drying, and penetrability. U.S. Pat. No. 4,732,613 to Shioya et al teaches multi-color printing from inks generally as contemplated by this invention and lists a number of di and tri propyl or higher alcohols. 1,2,6-hexanetriol is listed, but the 1,2 diol of butane or higher alkane is not listed.
U.S. Pat. No. 5,116,409 to Moffatt teaches a bleed alleviation mechanism employing a surfactant to form micelles. At least with respect to the C4 to C6 diols of this invention, this invention does not employ micelle formation, as shown by the absence of a sharp break in the surface tension versus concentration plots of inks of this invention.
The mechanism employed by this invention is increased penetration. Primary alcohols such as n-propanol, n-butanol and n-pentanol increase penetration and thus eliminate bleed, but for reasons such as flammability with the lower alcohols, odor, and higher volatility in the ink, these primary alcohols should be avoided or may be undesirable. The 1,2 diols of C4 and C10 have the same effect on penetration and thus bleed but are not flammable and may be used in inks without special precautions.